[vtkusers] read a vtp

[mariagrazia.madaschi at unibg.it]

I have to read a .vtp file to obtain points coordinates. I tried to use
the script below, but the result isn't right. Even if I write
reader.GetNumberOfPoint, instead of reader.GetOutput, the result is 0, but
is not true, because if I read the file with excel, number of points is
404442.
Where is the mistake in my script?
Is there any way to read points coordinates from a .vtp file?

(My problem is: I created a vtp with a group of kidney cells; every cells
is composed of many points. I need points coordinates to calculate the
centroid of every cells that I will use to build Voronoi diagram.)

import vtk

filename= "nuclei_1.vtp"

reader = vtk.vtkXMLPolyDataReader()
reader.SetFileName (filename)
polyDataOutput = reader.GetOutput()

print polyDataOutput